96 Missouri Agricultural Report. 



Polled Durham cross one of these combinations was white face and 

 no horns. But that is not all; some of these white faced calves 

 will be homozygote for white face ; that is, they will have inherited 

 this character from both parents ; others will be heterozygote. The 

 homozygotes will transmit white faces to all their progeny, while 

 the heterozygotes will transmit it to only half their progeny. The 

 total number of combinations in the second generation of the hybrid 

 is shown in figure 6. Here we have nine types, but they can not 

 all be distinguished by external characters. For instance, tj^jes 

 2, 3, 5, and 6 will all have white faces and no horns. But these 

 nine types aH differ in their inheritance, and hence no two of them 

 will transmit exactly the same characters to their offspring. The 

 most important point of all is that every one of the four visible 

 types shown in Fig. 4 is found absolutely pure in one of these 

 nine types. For instance, type 1 (Fig. 6) is homozygote for both 

 face color and horns. Similarly, types 3, 7 and 9 are all pure 



types and will reproduce true to type. We may, therefore, add to 

 the already important law of recombination the still more im- 

 portant fact that, in some individuals, if the progeny be numerous 

 enough, every possible combination of characters will be found in 

 a pure form that requires no further selection to fix its type. Noth- 

 ing more important than this has ever been discovered in the whole 

 realm of biology. 



This phase of the law is beautifully illustrated in some recent 

 work in the breeding of tomatoes done by Professors Price and 

 Drinkard of the Virginia Experiment Station, the results of which 

 I am now able to show you in the lantern slides. 



The parent plants used in making this cross differed in three 

 important characters. One of them had green leaves, the other 

 had yellowish leaves ; one had yellow fruit with a neck on it, rend- 

 ering it pear-shaped, the other had red fruit which was round, or 

 without neck. We thus have three character pairs, namely, green 



